delete doubly linked list in c code example

Example 1: delete function in a singly linked list in c

// A complete working C program
// to demonstrate deletion in
// singly linked list
#include <stdio.h>
#include <stdlib.h>
 
// A linked list node
struct Node {
    int data;
    struct Node* next;
};
 
/* Given a reference (pointer to pointer) to the head of a
   list and an int, inserts a new node on the front of the
   list. */
void push(struct Node** head_ref, int new_data)
{
    struct Node* new_node
        = (struct Node*)malloc(sizeof(struct Node));
    new_node->data = new_data;
    new_node->next = (*head_ref);
    (*head_ref) = new_node;
}
 
/* Given a reference (pointer to pointer) to the head of a
   list and a key, deletes the first occurrence of key in
   linked list */
void deleteNode(struct Node** head_ref, int key)
{
    // Store head node
    struct Node *temp = *head_ref, *prev;
 
    // If head node itself holds the key to be deleted
    if (temp != NULL && temp->data == key) {
        *head_ref = temp->next; // Changed head
        free(temp); // free old head
        return;
    }
 
    // Search for the key to be deleted, keep track of the
    // previous node as we need to change 'prev->next'
    while (temp != NULL && temp->data != key) {
        prev = temp;
        temp = temp->next;
    }
 
    // If key was not present in linked list
    if (temp == NULL)
        return;
 
    // Unlink the node from linked list
    prev->next = temp->next;
 
    free(temp); // Free memory
}
 
// This function prints contents of linked list starting
// from the given node
void printList(struct Node* node)
{
    while (node != NULL) {
        printf(" %d ", node->data);
        node = node->next;
    }
}
 
// Driver code
int main()
{
    /* Start with the empty list */
    struct Node* head = NULL;
 
    push(&head, 7);
    push(&head, 1);
    push(&head, 3);
    push(&head, 2);
 
    puts("Created Linked List: ");
    printList(head);
    deleteNode(&head, 1);
    puts("\nLinked List after Deletion of 1: ");
    printList(head);
    return 0;
}

Example 2: how to remove a node from a linked list in c

typedef struct node{
    int value; //this is the value the node stores
    struct node *next; //this is the node the current node points to. this is how the nodes link
}node;

node *rmvNode(node *head, int index){
    node *tmp = head;
    node *rmv;
    int count = 0;

    //base case for if the user enters a value greater then or equal to the length of the head
    //base case for if the user enters a value with a list of length 1. because in this library a list MUST contain one value minimum
    if(index >= len(head) || len(head) == 1){
        return NULL;
    }
  
    //if you want to remove the first value
    if(index == 0){
        rmv = head; //stores the head at this given moment in time
        head = tmp->next; //this jumps the position of the head making sure that the beginning is no longer part of the head
        free(rmv); //this frees the memory given to the initial head
        return head;
    }

    //if you want to remove index position 1
    if(index == 1){
        rmv = head->next;
        head->next = tmp->next->next;
        free(rmv);
        return head;
    }

    //if you want to remove the last value
    if(index == -1){
        
        while(count < len(head)-2){ //we do -2 because we want to access the node before the last one
            tmp = tmp->next;
            count += 1;
        }
        rmv = tmp->next;
        tmp->next = NULL;
        free(rmv);
        return head;
    }

    //remove anything else
    while(count < index-1){
        tmp = tmp->next;
        count += 1;
    }
    rmv = tmp->next;
    tmp->next = tmp->next->next;
    free(rmv);
    return head;

}